1. Field of the Invention
The invention relates to a fifth wheel including a coupling plate, a rotary joint and a preferably multipart sliding segmental lining which is rotationally fixedly arranged on the coupling plate and affords an upwardly directed sliding surface constituting an engagement surface for a semitrailer.
2. Description of the Related Art
Conventional fifth wheels are predominantly provided with sliding segments of steel whose sliding surface must be lubricated with grease in order to produce the desired frictional values and to avoid noise nuisance when two highly loaded steel surfaces frictionally slide against one another. A further disadvantage of this conventional fifth wheel construction resides in the temperature-dependent viscosity of the grease constituting the lubricant. At extremely low temperatures, for instance in use in arctic regions, the grease loses its lubricating properties; when used in hot areas the grease film rapidly breaks down and drips onto the road covering. The latter constitutes a heavy environmental burden which is difficult to tolerate.
Attempts have therefore been made to produce sliding segments for fifth wheels from special plastic mixtures which are supposed to ensure constant sliding characteristics between the trailer and coupling plate, even without lubrication. The load bearing capacity and stability of such lubricant-free sliding segments were previously not capable of being fully satisfactory.